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3D printed microscopes for as little as $2

Austrailian scientists have developed a way to create inexpensive lenses that cost less than a penny to produce. The new approach has allowed the team from the Australian National University (ANU) to build a 3D printed lens attachment that turns a smartphone camera into a dermascope, a tool to diagnose skin diseases like melanoma, which could be commercially available within the next few months.

The work, published in The Optical Society’s (OSA) journal Biomedical Optics Express on 24 April, could also be used in the future for applications such as scientific research in the lab, devices to detect diseases in the field, and optical lenses and microscopes for education in classrooms.

Many conventional lenses are made the same way lenses have been made since the days of Isaac Newton — by grinding and polishing a flat disk of glass into a particular curved shape. Others are made with more modern methods, such as pouring gel-like materials moulds. But both approaches can be expensive and complex, according to inventor of the technique, Dr Steve Lee from the Research School of Engineering at Australian National University (ANU).

With the new method, the researchers harvest solid lenses of varying focal lengths by hanging and curing droplets of a gel-like material—a simple and inexpensive approach that avoids costly or complicated machinery. ‘What I did was to systematically fine-tune the curvature that's formed by a simple droplet with the help of gravity, and without any moulds,’ said Lee.

Although it has long been recognised that a droplet can act as a lens, nobody has tried to analyse how effective of a lens it can be. Now, the team has developed a process that pushes this concept to its limits, Lee stated.

The process requires an oven, a microscope glass slide and a common, gel-like silicone polymer called polydimethylsiloxane (PDMS). First, a drop of PDMS is added onto the slide. Then, it is heated at 70°C to harden it, creating a base. Another drop of PDMS is added onto the base and turned over, and gravity pulls the new droplet down into a parabolic shape. The droplet is then heated again to solidify the lens. More drops can be added to hone the shape of the lens that also greatly increases the imaging quality of the lens. ‘It's a low cost and easy lens-making recipe,’ said Lee.

The researchers made lenses approximately a few millimetres thick, with a magnification power of 160 times and a resolution of about four microns. This is two times lower in optical resolution than many commercial microscopes, but more than three orders of magnitude lower in cost. ‘We're quite surprised at the magnification enhancement using such a simple process,’ Lee noted.

Their low cost — low enough to make them disposable — allows for a host of uses. ‘What I'm really excited about is that it opens up lens fabrication technology,’ said Lee. In particular, the researchers have built a lens attachment that turns a smartphone camera into a dermascope, a tool to diagnose skin diseases like melanoma. While normal dermascopes can cost $500 or more, the phone version costs around $2. The new dermascope, which was made using a 3D printer and is designed for use in rural areas or developing countries, is expected to be commercially available in just a few months, Lee pointed out. A similar smartphone-based tool can also help farmers identify pests out in their fields.

Prototype of 3D printed dermascope on a Smartphone (Nexus 4, Google) that consists of two LEDs (angled at 20o), a watch battery and a droplet lens. The attachment costs $2USD to make. Credit: Stuart Hay

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